Other

21st Meeting of the Irish Society of Human Genetics : Friday 21st September 2018 Croke Park, Dublin

Cosgrove D, Whitton L, Donohoe G, Morris D, Das S et al. · 1 Jan 2019

Abstract

Myocyte enhancer factor 2 C (MEF2C) is a transcription factor that plays a central role regulating cell differentiation, proliferation, survival and apoptosis. MEF2C has been implicated in each of the most recent GWAS of cognitive ability (CA) and educational attainment (EA). Animal studies have indicated that knockout of Mef2c interferes with healthy development of brain regions associated with cognitive function, e.g. hippocampal dentate gyrus, neocortex. Furthermore, mutation/deletion of MEF2C can cause severe intellectual and developmental disability. We therefore hypothesised that genes regulated by MEF2C would be associated with cognitive function. We created a set of differentially expressed genes (DEGs) based on an RNA-seq study that captured the transcriptional changes in mouse adult brain that result from early embryonic deletion of Mef2c in cortical and hippocampal excitatory neurons. This mouse DEG list was converted to human orthologues (n=1052) and tested for enrichment of genes associated with 1) CA, and 2) EA, using MAGMA and recent GWAS summary statistics for each phenotype. We also performed hypergeometric tests to investigate if the DEGs were enriched for current primary intellectual disability (ID), autism, and loss-of-function (LoF) intolerant (i.e. highly constrained) genes. We then used Ingenuity Pathway Analysis (IPA) to explore functional pathways implicated by the MEF2C DEGs. The DEGs were significantly enriched for CA (p=1.08e-07) and EA (p=9.88e-09) genes; along with ID (p=0.008), autism (p=0.001) and LoF intolerant (p=5.55e-21) genes. The top functions IPA predicted to be decreased from these DEGs are ‘development of neurons’ (p=5.41e-38, z-score=-2.0) and ‘formation of cellular protrusions’ (p=1.02e-28, z-score=-2.1). These findings indicate that genes influenced by MEF2C are highly constrained and contribute to cognitive function and neurodevelopmental disorders with severe cognitive deficits. Background & Aims: Newborn screening for Cystic Fibrosis (CF) commenced in the Republic of Ireland in July 2011. The aim of this study was to do a comprehensive review of the first five years, focusing on those who had CFTR genetic testing following an elevated IRT. Methods: This study included all neonates screened from July 2011 to June 2016. Data was expanded by cross-referencing patient charts, clinical and lab databases with the Non-NBS database to track down cascade tested relatives. Results: In this period a total of 342,424 infants were screened. 141 CF and 19 CF-SPID cases were identified in addition to 238 healthy carriers. 2 babies died from unrelated illnesses, before their Sweat Test. A total of 300/400 (75%) couples with a CF/CF-SPID/Carrier child were seen by a Genetic Counsellor. Phe508del was the most common mutation (79.9%) followed by Gly551Asp (8.7%). Consequently, 185/238 Carrier parents (78%) underwent genetic testing, identifying 1 carrier couple. 101/160 (63%) CF/CF-SPID parents were tested. 255 additional relatives came forward for cascade testing - 184 from 68/162 CF affected/CF-SPID/RIP families (42%), resulting in 3 new CF cases, 3 new CF-SPID cases and 64 additional carriers. Two cases were siblings born prior to NBS. One case was missed though NBS. 71 relatives from 33/238 Carrier families (14%) came forward for cascade testing, identifying a further 18 carriers. Conclusion: Through early detection of CFTR mutations, NBS provides the opportunity of early intervention and complication prevention as well as improvements in prenatal diagnoses and availability of cascade testing. Introduction: Interstitial deletions of 12q are rare with around 6 cases including 12q21 deletions described in the literature. We identified a male infant with 12q21.1-q21.33 deletion with phenotypic features including wide sandal gap and longitudinal plantar creases, short upturned nose, low set ears, feeding difficulties and delayed development. Methods: Array-CGH using the Agilent (ISCA*v2) 8x60K oligo array (genome assembly Build GRCh37) was undertaken on a chorionic villus sample at 13 weeks gestation due to raised nuchal translucency, and confirmed on venous blood after birth. A comparison of a-CGH microarray profiles was undertaken on the existing described cases. Results: Array-CGH confirmed a ~16Mb deletion containing nine OMIMMorbid genes ALX1 (OMIM *601527), BBS10 (OMIM *610148), CEP290 (OMIM *610142), DUSP6 (OMIM *602748), KITLG (OMIM *184745), MYF6 (OMIM *159991), OTOGL (OMIM *614925), PTPRQ (OMIM *603317) and TMTC3 (OMIM *617218). Using overlapping features of different 12q21 cases allowed microarray profiles to confirm a common deletion region including a non-morbid gene LIN7A. Its role encodes a scaffold protein within the CASK pathway which is important in synaptic function and is a possible responsible gene for the intellectual disability and cortical development present in all described cases. Parental a-CGH was normal confirming our case is de-novo. Conclusion: We delineate a 12q21 deletion syndrome with characteristic phenotypic features. LIN7A is a consistent deleted gene in this region and may be responsible for the intellectual disability due to cortical maldevelopment in this syndrome.